This invention is directed to an apparatus and process for the regeneration of an adsorber through which alternatingly flows raw gas and regenerating gas. An adsorbent is arranged in a container and the regenerating gas is conducted over the loaded adsorbent in an adsorber for conducting the process.
Adsorbers serve for the selective removal of one or several components from a raw gas to be purified. For this purpose, a raw gas is conducted over an adsorbent in which the components are adsorbed. The resultant gaseous mixture, freed of these components, is then discharged from the adsorber. After a specific time period, depending on the ambient conditions such as pressure, temperature, type and concentration of the impurities, as well as of the adsorbent, the adsorbent becomes loaded and is no longer capable of adsorbing additional gas. At this point, the feed of raw gas to the adsorber is cut off, and a regenerating gas is conducted over the adsorbent. The regenerating gas adsorbs the adsorbed components and carries them out of the adsorber. In order to ensure continuous operation, adsorbers are in most cases operated in pairs, wherein one of the adsorbers is always loaded while the other is being regenerated. As an example of such a process, a method for the adsorptive removal of moisture and carbon dioxide from air will be described as representative of many of the technical applications possible.
In many cases, the amount of regenerating gas available is limited. Thus, in order to obtain a useful regeneration of the adsorbent, the regenerating gas is heated. The temperature level of the regenerating gas depends, in addition to other factors, on the specific types of components to be removed from the raw gas. However, it has been found that, as a result of the relatively large heat capacity of the adsorbent container carrying the adsorbent, a temperature gradient results throughout the cross section of the adsorbent. Thus, the temperature of regenerating gas in the zone of the container wall is almost at ambient temperature levels, and reaches the highest temperature only near the center of the container. As a result, only a minor regeneration, or at least an inadequate regeneration, of the adsorbent occurs in the areas near the container wall.
The prior art has proposed elimination of the above-described problems by arranging a thin walled internal container of low heat capacity within the interior of the adsorbent container. The outer adsorbent container is built substantially pressure-proof, depending upon the occuring gas pressures and the static loads thereon and therefore, represents a large heat capacity.
The internal container is spaced from the walls of the outer container and is tightly connected to the outer container on one side. There are openings on the other side of the inner container establishing communication between the interior of the inner container housing adsorbent and the space between the outside internal container and the inside wall of the outer adsorbent container. This arrangement ensures that essentially the same pressure will prevail in the interior of the inner container and in the space between the inner container and the outer adsorbent container. Thus, the inner container is essentially pressureless because of the equalizing pressures on the outside and in the interior thereof. As a result, while the pressure in the container continues to act on the thick-walled, rugged outer container, the adsorbent is surrounded by the thin-walled internal container having a lower heat capacity. An adsorber of this type is shown in U.S. Pat. No. 2,083,732.
However, it has been found that such adsorbers exhibit a number of serious disadvantages. One major disadvantage is the great expense incurred in tightly connecting and sealing the internal container to the outer container. Even the smallest leak results in part of the gas to be purified flowing through the pressure equalizing openings and the space between the inner and outer containers. Thus, the portion of the gas flowing through said space will not be purified in the adsorbent in the interior container, because there is no adsorbent material in the space between the inner and outer diameters. Another disadvantage is that thermal stresses resulting from temperature differences between the high temperature regenerating gas and the low operating temperature, or a suddenly occurring pressure fluctuation on account of faulty switching operations when the automatic switching system fails, can lead to damage to the internal container.